Coupling system



15, 1932- w. VAN B. ROBERTS 1,872,343

COUPLING SYSTEM Filed Sept. 29, 1930 I ,2z i

a r 5 m swarm/a l l l- 4 m pur l- M mp0? INVENTOR WALTER VAN B. ROBERTS BY 7%W- ATTORNEY Patented Aug. 16, 1932 UNITED, STATES PATENT OFFICE V WALTER VAN B. ROBERTS, OF PRINCETON, NEW JERSEY, ASSIGNOR TO RADIO GOB- v, PORATION OF AMERICA, A. CORPORATION OF- DELAWARE COUPLING SYSTEM:

Application filed September- 29, 1930;. Serial No. 485,010.

The present invention relates to coupling systems, and more particularly to a novel screen grid tubes are utilized in each stage.

However, when such screen grid stages are coupled by the usual methods, the amplification tends to increase in value at higher fre quencie's. In fact, at very high frequencies, it becomes so great as to be uncontrollable, if it is of suflicient value at low frequencies.

Accordingly, it is one of the main objects of the present invention to provide a method of, and means for, coupling radio frequency circuits utilizing screen grid tubes, in such a manner that the amplification is effectively maintained constant regardless of the frequency of the currents transmitted from circuit to circuit.

Another important object of the invention is to provide a coupling arrangement between two stages of radio frequency amplification employing screen grid tubes, which arrangement comprises utilizing combined electrostatic and electromagnetic coupling between stages, and means, associated 'with the tuning means, for varying said electrostatic coupling.

Another object of the invention is to provide ina radio receiver means for coupling at least two stages of screen gridamplification, said means including a constant inductive coupling, and a variable capacitative coupling being secured by utilizing the capacity between a stator plate of predetermined shape connected to the plate of one tube and a stator plate of the tuning condenser in the input of the subsequent tube.

Still other objects of the invention are to improve generally the simplicity and efiiinparticularity in the appended claims, the

invention itself, however, as to both its organization and method of'operation will best be understoodby reference to the following description taken in connection with the drawing in which I have indicateddiagrammatically one circuit organization whereby my invention may be carried into effect.

In the drawing,

Fig. 1 shows diagrammatically a receiving circuit embodying my invention,

Fig. 2 is an electrical analysis of the invention. V

Referring to the accompanying drawing in which like characters of reference indicate the same parts in the diiferent figures, in Fig. 1 there is shown a conventional radio receiving circuit of the tuned radio frequency type embodying an antenna A, grounded as at G, and coupled, as at l, to the input electrodes of a screen grid tube 3. The anode of the tube 3'is energized from a source B, through the primary coil 4 of the coupling means 2, the latter providing a constant inductive coupling between the anode circuit of the 7 In securing this additional variable capa'citative coupling, I utilize the capacity existim between the last stator plate 10, and an additional, auxiliary plate 11, the latter plate being connectedby a lead 12 to a high potential point 13 in the anode circuit of the tube 3. The stator plate 10, in common with the remaining stator plates 10 of the vari-.

able tuning condenser 15, is connected by a lead 16 to a high potential point 17 in the grid circuit of the tube 4. The rotors 18 of the variable condenser 15, are all mountedon a single conductive shaft 20, as is well known to those skilled in the art, which shaft 15 C011.

nected by a lead 21 to the cathode of the tube 4.

As shown in Fig. 1, the rotor plate 1 8 disposed between the auxiliary plate 11, and the last stator plate 10 is adapted to vary the capacity between the plates 11 and 10, it being pointed out that the latter two plates are insulated from one another by an insulation block 22 disposed between the two. Thus, the auxiliary plate could really be an additional stator plate insulated from the group of commonly connected stator plates of the variable condenser. It will, therefore, be

appreciated that if the tuning of the input cir cuit of the tube 1 is varied, the additional capacitive coupling, which exists by virtue of the capacity between plate 11 in the output circuit of tube 3 and the stator plate 10 in the input circuit of the tube, is varied simul taneously. 1

In Fig. 2. there is shown the electrical equivalent of the invention employed in Fig. 1, the elements Land if v l being the leakage inductances of the primary coil 4 and the secondary coil 5 respectively, and the element M being the mutual inductancebetween the two coils a and 5. The tubes 3 and 4 havebeen shown in their proper position, the remaining portions of Fig. 1 not being essential to the electrical analysis of the coupling arrangement, having been omitted for the sake of simplicity of showing. The elements K, T, and C will be explained in the following explanation of the coupling arrangement.

Assume that the mutual inductance M is chosen to get the desired-amplification at long'wave length, the capacity C being then practically negligible due to the shielding action of rotor plate 18 and the capacity K being too small to be objectionable. If now the system is adjusted to operate at high frequency, if the capacity C were not changed the amplification would be so great as to be uncontrollable, but by increasing the capacity C a coupling of the opposite phase is introduced in increasing amount for partially wiping out the coupling effected by the mutual inductance M.

A proper value of the capacity C will reduce the amplification to the desired value. The value of the'capacity C required will be less the greater the leakage inductance L.

-By properly shaping the auxiliary plate 11, r the capacity Q can be made to vary in the desired fashion, as the rotor shaft 20 is turned. Itis-to-be noted that when the rotor plates 18 are entirely interleaved with the stator plates 10, the auxiliary plate ll is shielded from the stator plate 10 so that the capacity C isapproximately equal to zero. The existence of capacity K is incidental and variable, but does not affect the operation, except perhaps a trifle favorably at long waves.

It is pointed out that in radio frequency amplification circuits embodying screen grid tubes, this coupling method has particular utilityforthe reason that such tubes tend to givevery much greater amplification than ordinary tubes, so that it is more important to keep the amplification constant lest instabilitysetin at frequencies where the amplification' rises much above the minimum value, which value is set by considerationsof sensitivity.- y i l tis to understood that a plurality of coupling arrangements can be employed betweensucceedii'ig'pairs of tubes, and in such a case an auxiliary plate wouldbe disposed adjacent the stator plate of the variable condenser associated with the particularcircuit for which the variable condenser'is being used, and the common rotor shaft ofthe gang ofthevariable condensers would then be employed for simultaneously varying the capacities between all the auxiliary plates and their associated adjacent stator plates. Again, the coupling arrangement could be employed between the antenna and the input circuit of the first tube by replacing the plate of tube 3 in Fig. 1 by the antenna, and connecting the lower end of coil 4 to ground, instead of source B.- In such a case-tube 4 wouldof course become the first tube.

lVhile- I have indicated and described one arrangement for carrying my invention into effect, it will be apparent to one skilled in the art that my invention is by nomeans limited-tothe particular organization shown and described, but that many modifications may be inadewithout departing from the scope of my invention as set forth in the appended claims. p v :1'

--What I claim is: I

1. The combination of apair of space dis charge tubes including input and output circuits, means for tuning the input circuit of one of said tubes, capacitative and inductive couplings connected between the tuned input circuit and the output circuit of the other tube, said couplings being in phase opposition and the capacitative coupling being between the high potential ends of the tuned input circuit and the output circuit of said other tube, and means mechanically connected to, and operative with, the said tuning means to adjust the capacitative coupling as the input circuit of said one tube is tuned whereby the transfer of energy to said tuned input circuit is maintained independent of its frequency.

2. The combination of a pair of screen grid tubes including input and output circuits, means for tuning the input circuit of one of said tubes, capacitative and inductive couplings connected between the tuned input circuit and the output circuit of the other tube, said couplings being in phase opposition and the capacitative coupling being between the high potential ends of the tuned input circuit and the output circuit of said other tube, and means mechanically connected to, and operative with, the said tuning means to adjust the capacitative coupling as the input circuit of said one tube is tuned whereby the transfer of energy to said tuned input circuit is maintained independent of its frequency.

3. The combination of a pair of space discharge tubes including input and output circuits, means for tuning the input circuit of one of said tubes comprising a variable condenser, capacitative and inductive couplings connected between the tuned input circuit and the output circuit of the other tube, said couplings being in phase opposition and the capacitative coupling being between the high potential ends of the tuned input circuit and the output circuit of said other tube, and means mechanically connected to, and operative with, the said tuning means to adjust the capacitative coupling as the input circuit of said one tube is tuned whereby the transfer of energy to said tuned input circuit is maintained independent of its frequency.

4. The combination of a pair of space discharge tubes including input and output circuits, means for tuning the input circuit of 7 one of said tubes comprising a variable condenser, capacitative andinductive couplings connected between the tuned input circuit and the output circuit of the other tube, said couplings being in phase opposition and the capacitative coupling being between the "high potential ends of the tuned input circuit and the output circuit of said other tube, and means mechanically connected to, and operative with, the said variable condenser to adjust the capacitative coupling as the input circuit of said one tube is tuned whereby the transfer of energy to said tuned input cirpotential ends of the circuits being provided in opposing phase relation to the inductive coupling, said rotor member being so constru'cted and arranged with respect to the said capacitative coupling that adjustment of the rotor member simultaneously produces a predetermined adjustment of the capacitative coupling.

6. A coupling arrangement for an amplifier including a pair of screen grid tubes,

said arrangement comprising an output circuit between the output electrodes of one tube and an input circuit between the input electrodes of the other tube, a variable con-' denser for tuning the input'circuit including a rotor member, said circuits being induc tively coupled, capacitative coupling between the high potential ends ofthe circuits being provided in opposing phase relation to the inductive coupling, said rotor member being so constructed and arranged with respect to the said capacitative coupling that adjust' ment of the rotor member simultaneously produces a predetermined adjustment of the capacitative coupling, said capacitative cou- A pling being provided by the capacity existing between a pair of adjacent stators of said condenser.

7. A coupling arrangement for an amplifier including a pair of screen grid tubes, said arrangement comprising an output circuit between the output electrodes of one tube and an input circuit between the input electrodes of the other tube, a, variable condenser for tuning the input circuit including. a rotor member, said circuits being inductively coupled, capacitative coupling between the high potential ends of the circuits being provided in opposing phase relation to the inductive coupling, said rotor member being so constructed and arranged with respect to the said capacitative coupling that adjustment of the rotor member simultaneously produces a predetermined adjustment of the capacitative coupling, said capacitative coupling being provided by the capacity existing between a pair of insulated stators of said condenser.

8. A coupling arrangement for an amplifier including a pair of screen grid tubes, said arrangement comprising an output circuit between the output electrodes of one tube and an input circuit between the input electrodes of the other tube, a variable condenser for tuning the input circuit including a rotor member, said circuits being inductively coupled, capacitative coupling between thehigh potential ends of thecircuits being: provided in opposing phase relationto the inductive c0upling,. said vrotor member being so consimulated and arranged -1with' respectto the said capacitative Coupling that adjustment of the rotor membersimultaneously produces A a predetermined adjustment oithe capacitative coupling, a pair" of: spaced, insulated stator plates of said condenser providing said eapacitative Coupling, said rotor member having a rotor plate thereofrarranged for movement between said stator plates.

WALTER VAN B. ROBERTS. 

